United States Patent [191
[111
3,962,408
Dolezal
[451
June 8, 1976
[54]
DEHYDRATION 0F MAGNESIUM
3,241,915
3/1966
Moolenaar ........................ .. 423/498
CHLORIDE
3,471,250
10/1969
Langer .............................. .. 423/497
[75] Inventor: Henry Dolezal, Salt Lake City, Utah
[73] Assignee: The United States of America as
Primary Examiner-Edward Stern
Attorney, Agent, or Firm-Roland H. Shubert; Donald
represented by the Secretary of the
Interior, Washington, DC.
Filed:
July
14, 1975
[22]
[21] Appl. No.: 595,902
R. Fraser
[57]
ABSTRACT
A method for dehydrating magnesium chloride hy
drates or brines by complexing with amine hydrochlo
rides is described. Magnesium chloride hydrate or
[52]
[51]
US. Cl ................................ .. 423/498; 423/158
CO1F 5/30
and then at a more elevated temperature to decom
[58]
Field of Search .......... .. 423/498, 497, 158, 163
pose the anhydrous complex into anhydrous magne
sium chloride and amine hydrochloride. Any magne
Int. Cl.2 ...................... .. C01F 5/34; CO1F 5/32;
156]
1,389,546
1,557,660
1,661,894
References Cited
UNlTED STATES PATENTS
8/1921
10/1925
3/1928
sium oxides present in the starting material is con
verted to the chloride by reaction with the HCl
Dow .................................. .. 423/498
Cottringer et a1.
brine is reacted with an amine hydrochloride to form
a complex which is then heated to ?rst drive off water
.... .. 423/498
Griessbach ........................ .. 423/498
present.
9 Claims, N0 Drawings
3,962,408
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DEHYDRATION OF MAGNESIUM CHLORIDE »'
BACKGROUND OF THE INVENTION '-
2
ing essentially anhydrous magnesium chloride by ther
mal decomposition of the complex compound.
A further object of the invention is to employ as
amine hydrochlorides in the process the hydrochloride
This invention relates to the preparationv of' anhy- 5 salts of diethylamine, triethylamine, ethylenediamine,
drous magnesium chloride from its brines and hydrates.
aniline, pyridine, toluidene or picoline.
In the electrolytic production'of magnesium metal,
Further objects will become apparent from the fol
molten, substantially anhydrous magnesium chloride is
lowing speci?cation and claims.
employed as the electrolyte. Magnesium chloride is
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very' wat'er'soluble and crystallizes from solution as the 10
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SUMMARY OF THE INVENTION‘
hexahydrate, MgCl2.6H,O. Simple heating of the salt
does not result in dehydration to the anhydrousform.
Instead, MgQOClz an'd Mg(OH)2 are produced together
The process described and claimed herein comprises
contacting magnesium chloride hydrates or magnesium
chloride brine, which. may. have magnesium oxides
with HCI. Spray drying a hot saturated vsolution of mag-
present as impurities, with a hydrochloride of an amine
nesium chloride produces a product corresponding 15 of the class consisting of diethylamine, triethylamine,
approximately to MgCl2.2H2O and having about 1%
ethylenediamine, aniline, pyridine, toluidine or pico
Mg(Ol-l)2; see US. Pat. 2,381,994.
line. A complex of the amine hydrochloride and a mag
Various methods have been prepared for producing
nesium chloride hydrate is formed or if the brine is
anhydrous MgCl2. A number involve the chlorination
employed, a solution of the complex results.
of MgO or partially dehydrated MgClz. One method 20 The complex is heated to drive off the water, leaving
produces essentially water-free magnesium chloride
from the hexahydrate by thermal decomposition in a
an anhydrous product. Thereafter, no further heating,
the magnesium chloride-amine hydrochloride product
stream of hydrogen chloride gas. The presence of large
decomposes ‘into anhydrous magnesium chloride and
quantities of corrosive hydrogen chloride and the neamine hydrochloride. Any magnesium oxides present
cessity for maintaining essentially anhydrous condi- 25 are converted to magnesium chloride in the process.
tions are obvious disadvantges.
After the decomposition of the anhydrous complex, the
Another method which the subject of a number of
amine hydrochlorides are recovered for reuse. Produc
patents starts with ammonium camallite' and heats in
tion of the chloride'from magnesiumv oxides results in
two stages to drive off the water and then to fume off
the ,formation of the amine, which‘ is recovered and
the NH4CI. One drawback is that the ‘recovery and 30 convened to the hydrochloride salt by adding 'HCl.
reuse of the NH4Cl involves a sublimation step. Partial
'
decomposition or hydrolysis of the ammonium chloride
‘
results in the formulation of corrosive HCl. in a large
scale operation, this can present serious difficulties. '
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EXAMPLE I
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’ 105 parts of weight of MgClz, which may be'in
MgCl2.6H2O, MgCl2.4H2O, MgCl2.2H20 or in brine’, is
Pat. 2,381,994 showsheating a hydrous form‘of ma'g- 35 mixed with 130 parts’ by weight of aniline hydrochlo
nesiuni chloride with an alcohol to distill off the water
ride, in a 1.121 mol ratio, and heated at about 100°C.
and form solution of magnesium chloride from which
With the concentrated brine the excess water boils off
anhydrous MgCl2 is recovered. Pat. 3,241,915 com-
and hydrated double salts are formed. The equations
plexes hydrated MgCl2 with N,N dialkyvllarnides and ’
below depict the reaction.
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then decomposes the‘ complex to'r'ecover 'the why 45 With the hydrated salts, the reaction is similar,- except
drous salt.‘v Pat. 3,471,250‘ shows'comple'xing with various organic compounds containing S, O, P or N. How-
the excess water is not removed and the complex con
' tains the same water of hydration as the magnesium
ever, these patents do not show the formation of MgCl2
chloride hydrate starting material. On further heating
from any magnesium oxides which may be present. >
It is an object of this invention to produce essentially
water of hydration is progressively driven off until at
about 180°C, all the water of hydration is removed.
180°C
anhydrous magnesium chloride from magnesium chlo-
The steps depicted by equations (1) and (2) are carried
rides hydrates and brines employing an amine hydroout in one operation, although they may be conducted
chloride complexing agent and decomposing the comas separate discreet steps if desired.
plex compound to produce the anhydrous salt.
Any magnesium oxides present in the feed are chlori
Afurther object of this invention is to produce essen- 60 nated according to the following equation, at about
tially anhydrous magnesium chloride from hydrates
198°C:
and brines containing magnesium oxides by reacting
The aniline is condensed and reacted with HCl to form
with amine hydrochlorides to convert the oxides to the
chlorides, forming a complex compound and recover-
aniline hydrochloride, C6H5NH2HCl, for further use in
the process.
3,962,408
3
4
complex aniline magnesium chloride compound at an
for producing anhydrous magnesium chloride from
materials containing appreciable quantities of oxides
elevated temperature,,about 250°—320°C.
and oxychlorides.
Anhydrous MgCl2 is prepared by decomposing the
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' What is claimed is:
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_l. Atmethod, for dehydrating magnesium chloride
compositions comprising magnesium chloride, hydrates
or magnesium chloridebrineswhich comprises: >
,adding to said composition an vamine v“hydrochloride
of the group consisting of. diethylamine, triethyl
the liquid is used to complex additional magnesium
Chloride hydrates or brine_ EXAMPLE 2
l0
; amine, ethylene diamine, aniline,_;_ipyridine,,tolu
The process shown in Example‘ 1 was repeated‘ emidine‘ or-picolinehin a mole iratio'iof Mgclz: amine
ploying pyridine hydrochloride,C,,H,,N .HCl, instead of
hydrochloride of at least 1115
, ;
1
the aniline hydrochloride shown therein using the same
formmg 3; complex Qf,m?g§1¢s“!m QhI-QHde: hydrate
The aniline hydrochloride vapors are condensed'and
molar‘ ratio. The same results are obtained as with ani-
and mum hydrochloride?
.
r
_
-
line hydrochloride according to the following equation 15 [first heating said “complex to drive off water and
which corresponds to ( 1 ) to (4)_
I thereafter heating said‘ complex ‘at a more elevated
250-320
The molar ratios magnesium chloride ,to amine hydrochloride reactants may be from lzl to about 101,1;
,
Whileupper limit ratio maybe beyond lOzl, handling 30
temperature‘ to 'decompo'se'the' dehydrated com
plex into substantially anhydrous magnesium chlor
ide and aminehydroc‘hlo'ride, ’
‘ ~
' I 1 '
losses in reagent recovery and energy requirements for
the larger circulating load make the process uneco-
2. The method of claim {1 wherein vthe magnesium
chloride 'blrihes or hydrates contain oxygen compounds
nomical. ‘As .shown in,th_e equations, the magnesium
of magnesium and wherein said oxygen compounds
chloride .brine ‘or hydradye
heated-with, the amine
hydrochloride‘ to form a magnesium chloride-amine
react 'with'the amine hydrochlorides to‘ form magne
35 siumbhloridé.v
hydrochloridelcomplex, containing water of hydration.
The temperature is then raised-to drive off the water of
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' ' 3. The 'm'eth‘o'd of claim lv wherein the mol ratio‘of
MgyClg to ai'nineh'hydrochloride is’ about 1.1 to l. " ’
hydration and ‘thereafter the essentially anhydrous
' _4. The method ,IQf‘ClQiI‘hJ I wherein the amine hydro
magnesium chloride-amine hydroehloride'complex is
chlorideiis aniline 'hydrjochloridelx
decomposed by raising the temperature sufficiently
high to drive off the amine hydrochloride which is
v5. The method of claim 1 wherein theiamine hydro‘
chloride is pyridine hydrochloride.
condensed and recovered.
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Amine hydrochlorides other than aniline and pyridine hydrochloride may be employed in the process.
Theselinclude, but are not limited to,- the hydrochlo-
, .,
45
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6. The‘ method of claim 4 wherein the mol ratio» of
'MgClz to aniline hydrochloride is about 1:1 to l.
7. The method of claim 5 wherein the mol ratio of
MgClz to, pyridine hydrochloride?issaboutiL1 to l.
rides of diethylamine, triethy-lamine; ethylenediamine,
toluidine and-picoline.
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v8. The methods, of claim}, wherein the amine hydro
=
chloride is aniline hydrochlorideg
While the process has been described primarily ‘as
producing anhydrous magnesium chloride from brines
. ,
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9. The method of claim,2_ wherein the amine hydro
chloride is pyridine hydrochloride. 7
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andhydrates containing the same, it may be employed so .
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